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Long-term effects of fire frequency and season on herbaceous vegetation in savannas of the Kruger National Park, South Africa

Abstract

ABSTRACT
Aims:

The long-term effects of changing fire regimes on the herbaceous component of savannas are poorly understood but essential for understanding savanna dynamics. We present results from one of the longest running (>44 years) fire experiments in savannas, the experimental burn plots (EBPs), which is located in the Kruger National Park (South Africa) and encompasses four major savanna vegetation types that span broad spatial gradients of rainfall (450–700 mm) and soil fertility.

Methods:

Herbaceous vegetation was sampled twice in the EBPs using a modified step-point method, once prior to initiation of the experiment (1954) and again after 44–47 years. Different combinations of three fire frequency (1-, 2- and 3-year return intervals) and five season (before the first spring rains, after the first spring rains, mid-summer, late summer and autumn) treatments, as well as a fire exclusion treatment, were applied at the plot level (∼7 ha each), with each treatment (n = 12 total) replicated four times at each of the four sites (n = 192 plots total). The effects of long-term alterations to the fire regime on grass community structure and composition were analyzed separately for each site.

Important Findings:

Over the 44+ years duration of the experiment, fires were consistently more intense on sites with higher mean annual rainfall (>570 mm), whereas fires were not as intense or consistent for sites with lower and more variable rainfall (<510 mm) and potentially higher herbivory due to greater soil fertility. Because the plots were open to grazing, the impacts of herbivory along with more variable rainfall regimes likely minimized the effects of fire for the more arid sites. As a consequence, fire effects on grass community structure and composition were most marked for the higher rainfall sites and generally not significant for the more arid sites. For the high-rainfall sites, frequent dry season fires (1- to 3-year return intervals) resulted in high grass richness, evenness and diversity, whereas fire exclusion and growing season fires had the lowest of these measures and diverged the most in composition as the result of increased abundance of a few key grasses. Overall, the long-term cumulative impacts of altered fire regimes varied across broad climatic and fertility gradients, with fire effects on the grass community decreasing in importance and herbivory and climatic variability likely having a greater influence on community structure and composition with increasing aridity and soil fertility.


Ano de Publicação: 2013

Indigenous Burning as Conservation Practice: Neotropical Savanna Recovery amid Agribusiness Deforestation in Central Brazil

Abstract
International efforts to address climate change by reducing tropical deforestation increasingly rely on indigenous reserves
as conservation units and indigenous peoples as strategic partners. Considered win-win situations where global
conservation measures also contribute to cultural preservation, such alliances also frame indigenous peoples in diverse
ecological settings with the responsibility to offset global carbon budgets through fire suppression based on the presumed
positive value of non-alteration of tropical landscapes. Anthropogenic fire associated with indigenous ceremonial and
collective hunting practices in the Neotropical savannas (cerrado) of Central Brazil is routinely represented in public and
scientific conservation discourse as a cause of deforestation and increased CO2 emissions despite a lack of supporting
evidence. We evaluate this claim for the Xavante people of Pimentel Barbosa Indigenous Reserve, Brazil. Building upon
23 years of longitudinal interdisciplinary research in the area, we used multi-temporal spatial analyses to compare land
cover change under indigenous and agribusiness management over the last four decades (1973–2010) and quantify the
contemporary Xavante burning regime contributing to observed patterns based on a four year sample at the end of this
sequence (2007–2010). The overall proportion of deforested land remained stable inside the reserve (0.6%) but increased
sharply outside (1.5% to 26.0%). Vegetation recovery occurred where reserve boundary adjustments transferred lands
previously deforested by agribusiness to indigenous management. Periodic traditional burning by the Xavante had a large
spatial distribution but repeated burning in consecutive years was restricted. Our results suggest a need to reassess
overreaching conservation narratives about the purported destructiveness of indigenous anthropogenic fire in the cerrado.
The real challenge to conservation in the fire-adapted cerrado biome is the long-term sustainability of indigenous lands and
other tropical conservation islands increasingly subsumed by agribusiness expansion rather than the localized subsistence
practices of indigenous and other traditional peoples.

Citation: Welch JR, Brondı´zio ES, Hetrick SS, Coimbra CEA Jr (2013) Indigenous Burning as Conservation Practice: Neotropical Savanna Recovery amid Agribusiness Deforestation in Central Brazil. PLoS ONE 8(12): e81226. doi:10.1371/journal.pone.0081226

Ano de Publicação: 2013

Fire management in species-rich Cape fynbos shrublands

The management of fire-dependent biodiversity hotspots must be based on sound ecological knowledge and a
pragmatic approach that accommodates the constraints within which fire managers must operate. South Africa’s
fynbos biome (shrubland or heathland vegetation found in the Western Cape of South Africa) is one such
hotspot. In this region, the implementation of prescribed burning to conserve biodiversity must take into
account the area’s rugged and inaccessible terrain and recurrent wildfires, the presence of fire-adapted invasive
alien plants, and the imperatives for ensuring human safety. These constraints limit the potential for prescribed
burning to be effective everywhere, and prioritization and trade-offs will be needed to ensure the efficient use of
limited funding and management capacity. In such environments, management must be adaptive, based on
clearly defined and shared goals, monitoring, and assessment, and should be flexible enough to adjust as new
lessons are learned.

Ano de Publicação: 2013

Landscape structural analysis of the Lençóis Maranhenses national park: implications for conservation

Our work evaluated the anthropic effects on the landscape structure of the Lençóis Maranhenses National Park (LMNP) and its Buffer Zone, and proposed strategies for the region’s conservation. LMNP is an important protected area in Brazilian north coast which protects a unique wetland ecosystem composed of sand dunes fields and a coastal vegetation called restinga. Supervised mapping of LMNP and a surrounding buffer of 3 km was carried out through high resolution and fine scale (1:5000) satellite images. The mapped area was subdivided in 1000 ha hexagonal Analysis Units (AU) and the following landscape metrics were calculated for each one of them: cover area (CA) of each soil cover class - dune fields (CA-DUNES), water bodies (CA-WATER), dense restinga (CADENSE), scattered restinga (CA-SCATTER), grassland (CA-SANDY), mangroves (CA-MANG), anthropogenic activity (CA-ANTRO) and, secondary vegetation (CA-SECOND); Landscape Shannon Diversity Index (SHDI), and; percentage of native vegetation cover (NV−COV). Pearson correlations were performed between the CA of each class and SHDI to identify the classes most correlated to CA-ANTRO. Our results showed that anthropic classes (crops, trails, and villages) had a stronger correlation (Pearson Correlation, r ≈ 0.65) with phytophysiognomies of dense restinga, secondary vegetation and SHDI, thus indicating that the land use conversion occurs in dense restinga areas and promotes vegetation secondarization, as well as increasing fragmentation. At least, 42% of the dense restinga habitats was destroyed due to human activities. Five conservation and restoration strategies were proposed in a local scale depending on the percentage of native vegetation cover on each AU, from the most to less conserved: (a) only conservation; (b) conservation with management; (c) management; (d) management and restoration; and, (e) restoration. The implementation of Agroforestry Systems with agro-successional restoration goals was recommended as an alternative for land use.

Keywords:Land use, Territorial planning,Landscape metrics,Conservation strategies


https://reader.elsevier.com/reader/sd/pii/S1617138118303108?token=1E133DD41AB611A5DB97426EFB32BBDABC19DB7AD0359970DA0A6F9EDD129658E32C80E33214545E23956F5A37353057


Ano de Publicação: 2019

Can savanna burning projects deliver measurable greenhouse emissions reductions and sustainable livelihood opportunities in fire-prone settings?

Abstract

Savannas constitute the most fire-prone vegetation type on earth and are a significant source of greenhouse gas emissions. Most savanna fires are lit by people for a variety of livelihood applications. ‘Savanna burning’ is an accountable activity under the Kyoto Protocol, but only Australia, as a developed economy, accounts for emissions from this source in its national accounts. Over the past decade considerable effort has been given to developing savanna burning projects in northern Australia, combining customary indigenous (Aboriginal) approaches to landscape-scale fire management with development of
scientifically robust emissions accounting methodologies. Formal acceptance by the Australian Government of that methodology, and its inclusion in Australia’s developing emissions trading scheme, paves the way for Aboriginal people to commercially benefit from savanna burning projects. The paper first describes this Australian experience, and then explores options for implementing community-based savanna burning emissions reduction projects in other continental savanna settings, specifically in Namibia and Venezuela. These latter examples illustrate that savanna fire management approaches
potentially have broader application for contributing to livelihood opportunities in other fire-prone savanna regions.

Ano de Publicação: 2013

The Management of Fire-Adapted Ecosystems in an Urban Setting: the Case of Table Mountain National Park, South Africa

ABSTRACT.

The Table Mountain National Park is a 265-km² conservation area embedded within a city of 3.5 million people.
The highly diverse and unique vegetation of the park is both fire prone and fire adapted, and the use of fire forms an integral
part of the ecological management of the park. Because fires are both necessary and dangerous, fire management is characterized by uncertainty and conflict. The response of vegetation to fire is reasonably well understood, but the use of fire for conservation purposes remains controversial because of key gaps in understanding. These gaps include whether or not the vegetation is resilient to increases in fire frequency, how to deal with fire-sensitive forests embedded in fire-prone shrublands, and how to integrate fire and invasive alien plant control. National legislation emphasizes the need to protect communities from dangerous wildfires, and this compels fire managers to adopt a cautious approach to the application of fire. Ecological outcomes are optimized under a fire regime of relatively high-intensity, dry-season fires. Obtaining permission to burn under such conditions is not possible, and so the practice of prescribed burning is constrained, and this results in a fire regime dominated by wildfires. Ecological uncertainties, and the divergent requirements for maintaining healthy ecosystems on the one hand, and ensuring human safety on the other, result in a complex fire management environment. These complexities could be, and in some cases are being, alleviated by raising awareness, increasing fire management capacity, improving ecological monitoring of the effects of fire, and prioritizing areas for integrated fire and invasive alien plant management.
Key Words: biodiversity conservation; ecosystem management; forestry; fynbos; pines; wildland–urban interface

Ano de Publicação: 2012

The influence of prescribed fire on the extent of wildfire in savanna landscapes of western Arnhem Land, Australia

Abstract.

Fire regimes in many north Australian savanna regions are today characterised by frequent wildfires occurring
in the latter part of the 7-month dry season. A fire management program instigated from 2005 over 24 000 km2 of
biodiversity-rich Western Arnhem Land aims to reduce the area and severity of late dry-season fires, and associated
greenhouse gas emissions, through targeted early dry-season prescribed burning. This study used fire history mapping
derived mostly from Landsat imagery over the period 1990–2009 and statistical modelling to quantify the mitigation of
late dry-season wildfire through prescribed burning. From 2005, there has been a reduction in mean annual total proportion
burnt (from 38 to 30%), and particularly of late dry-season fires (from 29 to 12.5%). The slope of the relationship between
the proportion of early-season prescribed fire and subsequent late dry-season wildfire was,–1. This means that imposing
prescribed early dry-season burning can substantially reduce late dry-season fire area, by direct one-to-one replacement.
There is some evidence that the spatially strategic program has achieved even better mitigation than this. The observed
reduction in late dry-season fire without concomitant increase in overall area burnt has important ecological and
greenhouse gas emissions implications. This efficient mitigation of wildfire contrasts markedly with observations reported
from temperate fire-prone forested systems.
Additional keywords: fire management, greenhouse gas emissions, Leverage, planned fire, unplanned fire.

Ano de Publicação: 2012

Savanna burning: The ecology and economy of fire in tropical savannas

Tropical savannas are the world’s most fire-prone biome, making fire a key issue for the maintenance of savanna ecosystem function and for the management of savanna biodiversity. Savanna burning also makes a significant contribution to global greenhouse gas emissions, through its effects on emissions of methane and nitrous oxide, and on carbon sequestration. There is growing international interest in reducing the extent and severity of savanna fires in the context of greenhouse gas abatement. Fire management for greenhouse gas abatement is a particularly important issue for northern Australia, where the burning of >400 000 km2 each year contributes on average 3% of Australia’s accountable greenhouse gas emissions.
Most of these emissions are produced by relatively highintensity wildfires that sweep through remote and unmanaged
areas during the end of the dry season, and which seriously threaten iconic biodiversity values such as those of World Heritage-listed Kakadu National Park. Greenhouse gas abatement provides an economic basis for improved fire management in these remote areas. It also presents important livelihood opportunities for remote Aboriginal communities, where traditional knowledge relating to fire remains strong, as does the desire to re-establish traditional fire management practices on their homelands. Savanna burning, therefore, sees an unprecedented meeting of interests relating to biodiversity protection, greenhouse gas abatement, and culturally appropriate economic opportunity for historically marginalized communities. This calls for an interdisciplinary understanding of fire in savanna landscapes, incorporating fuel dynamics and fire behaviour, the effects of fire on biodiversity and ecosystem function, economic analysis, and indigenous livelihood
development. Such is the scope of this Special Issue. The Special Issue begins by addressing the drivers of fire
occurrence in a Neotropical savanna (Hoffmann et al. 2012).This is followed by papers on fire and tree dynamics
in Australian savannas (Bond et al. 2012; Werner 2012), focussing on the peculiar ability of eucalypts to ‘escape the
fire trap’. There is considerable interest in the extent to which long-term fire exclusion can result in a biome shift
from savanna to forest, and this issue is addressed by Scott et al. (2012) in a northern Australian case study. Cook
(2012) addresses fire management in the context of fuel and savanna vegetation dynamics in landscapes undergoing
restoration following broad-scale mining.The effects of fire on soil nitrogen are examined by Richards et al. (2012b), while Andersen et al. (2012) and Radford and Andersen (2012) address fire in relation to fauna conservation in northern Australia.The Special Issue concludes with a spatially explicit economic analysis of fire management for greenhouse gas abatement across northern Australia (Heckbert et al. 2012), and a northern Australian case study integrating the ecological and economic consequences of different fire management options in the context of indigenous livelihood development (Richards et al. 2012a). We are hopeful that this Special Issue will provide an enhanced understanding of the full ecological, economic and social values of fire management in savanna landscapes.

Ano de Publicação: 2012

Savanna burning for biodiversity: Fire management for faunal conservation in Australian tropical savannas

Abstract

Tropical savannas are the world’s most fire-prone biome, and savanna biotas are generally well adapted
to frequent fire. However, in northern Australia there are concerns that recent increases in the frequency and extent
of high-intensity fires are causing substantial declines in regional biodiversity values. In this paper we use two
well-studied and contrasting faunal groups, ants and small mammals, as case studies for reviewing faunal responses
to fire in Australian savannas.The Australian savanna ant fauna is dominated by arid-adapted taxa that are highly
resilient to frequent fire and are not considered to be threatened by prevailing fire regimes. Indeed, frequent fire
promotes ant diversity because it maintains an open habit that makes the dominant arid-adapted taxa feel at home.
Long-term fire exclusion reduces ant diversity due to a marked decline in arid-adapted taxa, and favours highly
generalized, more shade-tolerant taxa. In contrast, many small mammal species of high conservation value are
highly sensitive to frequent fire, and there are widespread concerns that their populations are threatened by current
fire management. Many of the species have shown dramatic population declines over recent decades, and, although
the causes are poorly understood, there is little doubt that fire is an important contributing factor. It is likely that
fire is acting synergistically with other underlying causes of decline, particularly predation by feral cats.The overall
resilience of most savanna animal species in relation to frequent fire suggests that they are secure under all but the
most extreme fire regimes. However, it is clear that more fire-sensitive groups such as small mammals need special
fire management attention.This needs to involve less frequent and finer-scale burning, along with the protection of
some large, infrequently burnt source areas.
Key words: ant, fire regime, fire resilience, frequent fire, small mammal.

Ano de Publicação: 2012

Growth of juvenile and sapling trees differs with both fire season and understorey type:Trade-offs and transitions out of the fire trap in an Australian savanna

Abstract

Canopy tree populations in mesic savannas are often bimodal with few saplings but many smaller individuals of indeterminate age that repeatedly suffer topkill and regenerate from underground tissues. Little is known about growth rates or mechanisms that allow subadult trees to reach the canopy. The wooded savannas of northern Australia have high frequencies of dry-season fires. In a 32 400-m2 field experiment, 2405 juveniles (<150-cm height) and saplings (150–499 cm) of the eucalypt canopy species were individually marked and measured the year prior to fires set in three different seasons and again at the end of the growing season (without fires) a year later.Trees in unburnt plots served as controls. All fire treatments were repeated in plots dominated by the most common understorey, a native annual grass (sorghum) and in plots dominated by perennial native species; these produce different fuels for fires and competitive regimes for young trees. After early dry-season fires, height growth of larger juveniles and all saplings was significantly enhanced, especially in sorghum. After late dry- or wet-season fires, juvenile trees grew well, but all of the small saplings (150- to 299-cm height) were reduced to ‘juveniles’ and did not recover pre-fire heights but, instead, produced many new basal (coppice) stems. Late, dry-season fires reduced more than 80% of large saplings (300–499 cm) to juvenile size in sorghum, whereas in non-sorghum, 60% of the trees grew to poles (500–999 cm). The results demonstrate that juvenile and sapling growth responses to fire and the probability of subadult trees reaching the canopy are related to fire–understorey interactions, and suggest that the mechanisms include morphological and carbohydrate storage dynamics which vary with tree size and life history stage. The key to successful management of a sustainable woody canopy lies in the understorey.
Key words: Eucalyptus population dynamics, fire: effect of fire season, fire–understorey interaction, savanna
woodland: tree: height growth, tree: canopy replacement.

Ano de Publicação: 2012